“The point wasn’t American casualties”
Yes, the point was the American casualties.
Okinawa was a shock as American losses were an order of magnitude higher than at Iwo Jima. And, as I’ve already demonstrated, allied losses at Iwo Jima were considered high for the war. Do I need to cite contemporary opinion stating exactly this?
Okinawa in May after VE day was followed up by the push (by Truman) for the Trinity experiment, followed by the subsequent dropping of the bomb on Japan. The timeline fits together well. It matches up with contemporary opinion of the shock of the American battle losses at Okinawa being larger than the entire rest of the war in the pacific up to that time.
The historical account simply doesn’t support your position, sorry. Okinawa was a shock.
A. The Manhattan Project was started in 1942, specifically with Germany in mind. It doesn't matter how much you wish it were otherwise, Germany was the intended first recipient in mind.
B. The Manhattan Project - started in 1942, with Germany as the primary target - culminated with the successful Trinity test in July 1945, but sadly, Germany had surrendered in May 1945.
C. It took years to develop the weapons used at Hiroshima and Nagasaki and Okinawa had absolutely nothing to do with it other than to galvanize the American determination to crush Japan and end the freakin' war.
D. Truman inherited a nearly-completed nuclear program in April 1945 - he didn't push anything. He didn't even know about the Manhattan Project until April '45.
5. If they had developed the nukes in one or two years, instead of three, Germany would have gotten it right in the neck.
Pick a stat would you? More casualties at Oki, much bigger battle. The US casualty rate at Iwo exceed the number of enemy that were there in a much shorter timeframe.